| Contents |
| We consider partial differential equations admitting peaked soltion solutions (peakons), and give a survey of results on the integrability of such equations. Some of the properties of peakons are related to their shape, which is inherited from the one-dimensional Helmholtz operator. Green's functions for other operators are considered, in particular in an economic model for urban growth due to Krugman, where integrability is absent, but exact results on the long-term evolution of the system are still possible. |
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